Wafer-level packaging (WLP) is to package an integrated circuit (IC) at wafer level, which is essentially a true chip scale package (CSP) technology, because the resulting package is practically of the same size as the die. In general, the formation of a packaged semiconductor device with under-bump metallurgy (UBM) between a solder bump and a redistribution line (RDL) requires three or four lithographic level masks, and has higher fabrication cost. A packaged semiconductor device containing no UBM between a solder bump and a RDL can lower fabrication cost, because only two lithographic level masks are required for manufacturing the UBM-free packaged semiconductor device. However, in the UBM-free packaged semiconductor device, the solder bumps (balls) are directly mounted on the RDLs, and thus a ball shift problem is likely to be caused during a ball mount process. The ball shift problem results in an inclined printed circuit board mounted on the solder bumps, and degrades the board-level temperature cycling (TC) performance of the device, thus inducing low yield of the ball mount process.